1. Field of the Invention
The present invention relates to a flat plate heat pipe and a method for manufacturing the same, and in particular to a flat plate heat pipe in which a sintered supporting layer is provided and a method for manufacturing the same.
2. Description of Prior Art
With the advancement of science and technology, the amount of heat generated by an electronic component during its operation is increased greatly. Thus, it is an important issue for the electronic industry to solve the problems relating to the cooling or heat dissipation of the electronic components. Further, in view of the requirements for high efficiency, integration and versatility of the electronic components, the manufacturers in the electronic industry aims to increase the heat transfer efficiency.
A heat sink is often used to dissipate the heat of an element or system to the outside. In case of a smaller thermal resistance, the heat-dissipating efficiency of the heat sink becomes larger. In general, the thermal resistance of the heat sink is constituted of a spreading resistance within the heat sink and a convection resistance between the surface of the heat sink and ambient atmosphere. In practical applications, materials of high thermal conductivity such as copper or aluminum are used to manufacture the heat sink to thereby reduce the spreading resistance. However, the convection resistance is still so large that it undesirably restricts the performance of the heat sink. As a result, the heat-dissipating efficiency of the heat sink cannot conform to requirements for the heat dissipation of new-generation electronic elements.
As mentioned in the above, in order to enhance the heat-dissipating efficiency, various kinds of heat pipes and vapor chambers with high thermal conductivity are developed to be assembled with a heat sink.
The heat-dissipating principle of the vapor chamber is substantially the same as that of the heat pipe. A working fluid is filled in the vapor chamber having an evaporating surface and a condensing surface opposite to the evaporating surface. The evaporating surface is brought into contact with a heat source to absorb the heat of the heat source, thereby heating and evaporating the working fluid in the vapor chamber. When the vapor is brought into contact with a cold surface (i.e., the condensing surface), the vapor condenses into liquid to release the latent heat. With the phase change between vapor and liquid of the working fluid, the heat of the heat source can be conducted to the condensing surface.
Please refer to FIG. 1. The conventional flat plate heat pipe is constituted of a first copper plate 10 and a second copper plate 11. The first copper plate 10 is connected to the second copper plate 11 to define a chamber 12 there between. The chamber 12 is filled with a working fluid such as water or other suitable liquid. Two opposing surfaces of the first copper plate 10 and the second copper plate 11 are formed with a wick structure 13 respectively in such a manner that the inner surfaces of the chamber 12 are coated with the wick structure 13. Conventionally, the primary functions of the wick structure 13 are as follows: the amount of heat passing through the wall of the vapor chamber is reduced; the total area for evaporating the working fluid is increased; and the growth of vapor film is prevented due to the contact of the wick structure and the wall of the chamber. Due to gravity and capillary force of the working fluid, the working fluid is distributed in the wick structure 13 inside the chamber 12 (i.e. the wick structure 13 provided on the first copper plate 10 and the second copper plate 13).
The outer surface of the first copper plate 10 opposite to the chamber 12 is brought into contact with a heat-generating element (such as a central processor). At this time, the first copper plate 10 is referred to as an evaporating end, whereby the heat generated by the heat-generating element is conducted to the second copper plate 11 (referred to as a condensing end) for heat dissipation. Thus, the heat generated by the heat-generating element is absorbed by the first copper plate 10, thereby heating and evaporating the working fluid on the wick structure 13.
Thereafter, the vapor quickly flows toward a colder place (i.e. the second copper plate 11) where the vapor releases its latent heat and condenses into liquid. By means of the capillary force of the wick structure 13 on the second copper plate 11, the condensed droplets of the working fluid flow back to the first copper plate 10. With this circulation of the working fluid, the heat of the heat-generating element can be dissipated.
However, during the phase change of the working fluid between vapor and liquid, the working fluid flowing in the wick structure 13 may cause some problems as follows. (1) Although the increase of the heat flux also raises the phase-changing speed of the working fluid, the amount of working fluid flowing back to the evaporating end is insufficient because the tiny pores and low permeability of the wick structure may hinder the working fluid from flowing back to the evaporating end. As a result, the evaporating end of the heat pipe may be dried out to deteriorate its heat-dissipating efficiency. (2) When the heat flux continuously increases to such an extent that the vapor pressure is larger than the liquid pressure, vapors or bubbles may be generated in the wick structure to hinder the working fluid from flowing back to the evaporating end. Then, a film of vapor having a large thermal resistance is generated between the evaporating end and the wick structure, so that the heat absorbed by the evaporating end cannot be taken away by the working fluid smoothly. As a result, the heat is continuously accumulated in the evaporating end, so that the evaporating end of the heap pipe is dried out to deteriorate its heat-dissipating efficiency.
According to the above, the conventional flat plate heat pipe has drawbacks as follows;
(1) Since the casing of the heat pipe is constituted of an upper plate and a lower plate, four sides of the upper plate and the lower plate are soldered to form a sealed casing. Thus, the actual working space available for accommodating the working fluid will be inevitably reduced due to the soldered sides of the upper plate and the lower plate.
(2) Since four sides of the upper plate and the lower plate have to be soldered together to form a sealed casing, the process is no doubt time-consuming with a higher production cost.
Therefore, the present inventor and the manufacturers in this filed to solve the above-mentioned problems in prior art.